Turbine starter and cooling



Nov. 22, 1966 D. JOHNSON TURBINE STARTER AND COOLING 2 Sheets-Sheet 1 Filed July 22, 1965 m T m V N I Nov. 22, 1965 D- JOHNSON TURBINE STARTER AND COOLING 2 Sheets-Sheet 3 Filed July 22, 1965 United States Patent Ofiice 3,286,461 TURBINE STARTER AND COOLING Douglas Johnson, Indianapolis, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed July 22, 1965, Ser. No. 474,000 6 Claims. (Cl. 6039.14)

My invention is directed to improve cooling of the turbines of gas turbine engines. It is particularly adapted to prevent overheating of the turbine during starting ofv the engine and involves what I believe to be a new combination between the use of air for starting the engine and an arrangement for air cooling the rotor of the turbine.

The nature of the invention and the advantages thereof will be apparent to those skilled in the art from the succeeding detailed description of the preferred embodiment of my invention.

FIGURE 1 is a side view of a gas turbine engine of a turbofan type, with parts cut away.

FIGIURE 2 is a sectional view through the outer part of the high pressure turbine of the engine, taken on a plane containing the axis of rotation of the turbine.

FIGURE 3 is a view similar to FIGURE 2 taken on a different plane.

FIGURE 4 is a fragmentary view taken on still another plane containing the axis of the turbine.

In general, the invention is applicable to gas turbines of various types; therefore, the lift engine in which it has been embodied will not be described in detail. The engine E is generally cylindrical in contour, including an outer shell *6 and a turbine outer case 7 which define between them the exhaust duct from a fan (not illustrated) in the forward part of the engine. The for- Ward part of the engine in addition to the clan includes a compressor "(not shown) which forces air through cornbustion apparatus, a high pressure turbine '8 which drives the compressor, and a low pressure turbine 9 which drives the fan. The turbines exhaust through a duct 11 within the wall 7. The rear part of the combustion apparatus is shown :at 1-2 in FIGURE 1.

Referring to FIGURES .2 and 3 for .a more detailed showing of the significant parts of the turbine 8, there are illustrated two sections 14 and 15 of the turbine case 7 which are joined by bolts 17. The bolts 17 also mount a turbine exhaust shroud 18. A diaphragm 19 is mounted on this shroud. Struts 20 extending from the case 7 to a bearing support 21 are connected to the outer 'shell '6 by struts 22 (FIGURE 1). Turbine 8 comprises a wheel 23 bearing blades 25. Combustion gases are directed to the wheels by an annular nozzle 26 comprising an outer shroud ring 27, an inner shroud ring 28, and radially disposed hollow vanes 29. The vane-s may be cast with the shrouds 27 and 28, which may be segmented. The outer shroud 27 also provides a stationary shroud cooperating with the tip shrouds of blades 25. The rear end of shroud 27 pilots within a flange on shroud 18.

The portion 14 of the engine case is the outer wall of an annular combustion apparatus jacket and the inner wall of the combustion apparatus is defined by an annular structure 31 which is connected to an inwardly directed flange 32 of the inner shroud 28 with freedom for radial expansion. The engine includes an annular combustion liner defined by an outer wall 34 and an inner wall 35, these wall having a tongue-and-groove fit with the forward edges of the nozzle shrouds 27 and 28, respectively. Thus, the combustion gases generated within the combustion liner are directed through the nozzle 26 onto blades 25 and then flow through the shroud 18 into the low pressure turbine 9 and to exhaust.

3,286,461 Patented Nov. 22, 1966 With this introduction, we may proceed to a more detailed consideration of the structure of the turbine which provides for cooling during starting as well as during normal running of the engine. Considering first the turbine rotor, the blades 25 have serrated or dovetail roots 37 mounted in grooves across the rim 38 of the turbine wheel. A stalk 39 connects the root 37 to the airfoil portion 41 of the blade. A platform 42, and a lip 43 extend circumferentially from the blade into contact with corresponding structures on the adjacent blades. A seal ring 45, which may be segmented, is mounted on the rear face of the wheel with its inner portion abutting the rear face of rim 38 .and its outer portion lying behind the stalks 39. Seal 45 includes a ridge 46 which acts as a labyrinth seal in cooperation with the inner wall of exhaust shroud 1 8. An expanding ring 47 engaging in a groove 48 in the rim retains the seal 45. This structure of the rotor defines a path for flow of cooling air through the gap 49 between the lip 43 and the rim of the wheel and out through the narrow gap 50 between the seal 45 and platforms 42. Since this path has an outward radial component, the air is subjected to pumping by rotation of the turbine wheel.

Considering now the stationary structure associated with the turbine nozzle 26, :a ring 5-2 fixed to shroud 27 ahead of the blades and lying outwardly of shroud 27 terminates in a flange 53 which is held between the flanges of combustion chamber jacket 14 and exhaust shroud 1'8 and serves as a support for nozzle 26. The nozzle shroud 27, ring 5 2, and the forward portion 55 of shroud 18 define an annular plenum chamber 57 to which air or other gas under pressure is admitted for starting the engine. Bosses 58 on the shroud 27 are drilled to provide numerous nozzles 59 more or less tangential to the engine axis through which starting air is discharged against the blades 25 to start the engine by the well-known air impingement method of starting. The structure by which air is admitted to plenum 57 is immaterial to the invention and is indicated schematically on FIGURE 2 by compressed starting air line 61, a shutoff valve 62, and the connection '63 into the plenum 57.

For starting the engine, with line 61 connected to any suitable source of compressed air, valve 62 is opened and the air supplied to plenum 57 flows through nozzles 59 against the blades 25, thus rotating the engine up to starting speed. I realize that this mode of starting an engine is known, but as will be seen, this is associated with means for cooling the engine during starting and running. The passages 65 through the hollow vanes 29 connect plenum 57 to a manifold 66 at the inner ends of vanes 29. This manifold is defined by shroud 28, its flange 32, and a cylinder 67 which is welded or otherwise fixed at its edges to the shroud 28. A large number of cooling nozzles 70 (FIGURE 3) and 71 (FIGURE 4) are distributed around the circumference of the turbine nozzle 26, being welded to prismoidal blocks 72 and 73, respectively, Welded to the flange 32 and cylinder 67. In a large engine there may be about 60 cooling nozzles. The nozzles 71 are preferably about twice as numerous as the nozzles 70. These differ from each other in the source of cooling air supplied to them. The mounting blocks 72 define passages 74 extending into the manifold 66 so that, when air is supplied to plenum 57 during starting of the engine, it is also delivered to nozzles 70 and through them to the spaces beween the stalks 39 of the turbine blades. The flange 32 is bored with a relatively large number of small air metering holes 76. In the engine illustrated, there are seventy-two such holes distributed around the circumference of the nozzle connecting the manifold 66 with the combustion chamber jacket. Thus,

during starting of the engine some of the starting air, about ten percent, bleeds through these holes 76 into the combustion apparatus. However, once the engine is started and compressor discharge pressure builds up, combustion chamber jacket air flows through holes 76 into the manifold 66 and thus through nozzles 70 and also through vanes 29 into plenum 57 and out through nozzles 59.

The cooling air nozzles 71 (FIGURE 4) which are distributed between the nozzles 70 are in direct communication with the combustion chamber jacket through drilled passages 78 in the mounting blocks 73. Thus, combustion chamber jacket air is also blown through these at the turbine blade stalks when the engine is in operation.

A brief review of the operation will make it clear that the cooling system described provides some cooling of the turbine nozzles and very effective cooling of the rotor rim and blades, during starting of the engine, where abnormal heating conditions may be encountered, and during normal running when the engine is operated at high temperatures. During starting, compressed air is discharged from nozzles 59 onto the outer ends of the turbine blades; it circulates through passages 65 of vanes 29, thus cooling these slightly. The starting air also cools the shrouds 27 and 28 to some extent. The air discharged from manifold 66 through nozzles 70 flows into the gap 49, past the blade stalks and out through the gap 50 into the turbine exhaust. Thus, the blade stalks and indirectly the inner portion of the blade and the wheel rim are cooled. After the start has progressed to the point that the engine is self-sufficient and the starter air valve 62 is closed, the turbine is still cooled by combustion chamber jacket air metered through holes 76. This air is hot, but it is much cooler than the motive fluid. Metered air flowing through holes 76 into manifold 66 flows radially outwardly through the vanes and through nozzles 59 to the outer portion of the blades, thus cooling the turbine nozzle and the blade tips. The air discharged directly from the combustion chamber jacket through nozzles 71 and that discharged by way of manifold 66 through nozzles 70 is blown against the blade stalks and pumped into the turbine exhaust. It will be seen that distribution of cooling under both these conditions may be varied to suit the needs of a particular installation by the relative sizes and numbers of nozzles 59, holes 76, and the tips 80 andSl of cooling nozzles 70 and 71, respectively.

Since plenum 57 and manifold 66 are in wide-open communication with each other, they may be regarded as a single air chamber from which air is directed to the turbine rotor for starting and cooling.

The detailed description of the preferred embodiment of the invention for the purpose of explaining the principles thereof is not to be considered a limiting or restricting the invention, as many modifications may be made by the exercise of skill in the art.

Iclaim:

1. An air-cooled gas turbine comprising, in combination,

a turbine wheel bearing blades on its periphery a turbine nozzle adapted to direct motive fluid to the blades combustion apparatus supplying motive fluid to the turbine nozzle including an air jacket supplied with compressed air when the turbine is in operation means defining an air chamber turbine air impingement starting nozzles supplied from the chamber turbine cooling nozzles supplied from the chamber located to direct cooling air at the turbine wheel valved means for supplying compressed gas to the chamber for starting the engine and metering orifice means constantly connecting the combustion chamber air jacket to the chamber.

2. An air-cooled gas turbine comprising, in combination,

a turbine wheel bearing blades on its periphery a turbine nozzle adapted to direct motive fluid to the blades combustion apparatus supplying motive fluid to the turbine nozzle including an air jacket supplied with compressed air when the turbine is in operation means defining an air chamber turbine air impingement starting nozzles supplied from the chamber turbine cooling nozzles supplied from the chamber located to direct cooling air at the blades adjacent the wheel valved means for supplying compressed ga to the chamber for starting the engine and metering orifice means constantly connecting the combustion chamber air jacket to the chamber.

3. An air-cooled gas turbine comprising, in combination,

a turbine wheel bearing blades on its periphery a turbine nozzle adapted to direct motive fluid to the blades combustion apparatus supplying motive fluid to the turbine nozzle including an air jacket supplied with compressed air when the turbine is in operation means defining an air chamber turbine air impingement starting nozzles supplied from the chamber turbine cooling nozzles located to direct cooling air at the blades adjacent the wheel valved means for supplying compressed gas to the chamber for starting the engine and metering orifice means constantly connecting the combustion chamber air jacket to the chamber some of said cooling nozzles being supplied from the chamber and others of said cooling nozzles being supplied directly from the air jacket, bypassing the chamber.

4. A gas turbine engine comprising, in combination,

a turbine wheel blades mounted on the rim of the wheel a turbine nozzle including a ring of radially extending vanes disposed upstream of the blades combustion apparatus including a jacket terminating at the nozzle and a combustion liner connected to discharge through the nozzle the nozzle including a hollow outer shroud defining a lenum and a hollow inner shroud defining a manifold the vanes defining passages interconnecting the plenum and the manifold impingement starting nozzles in the outer shroud supplied from the plenum and discharging generally tangentially against the outer end of the blades a ring of cooling nozzles mounted on the inner shroud and discharging adjacent to the base of the blades means defining air metering passages openings in the inner shroud connecting the interior of the jacket to the manifold and means defining passages through the inner shroud connecting the said cooling nozzles to the manifold.

5. A gas turbine engine comprising, in combination,

a turbine wheel blades mounted on the rim of the wheel a turbine nozzle including a ring of radially extending vanes disposed upstream of the blades combustion apparatus including a jacket terminating at the nozzle and a combustion liner connected to discharge through the nozzle the nozzle including a hollow outer shroud defining a pltleriium and a hollow inner shroud defining a manithe vanes defining passages interconnecting the plenum and the manifold impingement starting nozzles in the outer shroud supplied from the plenum and discharging generally tangentially against the outer end of the blades a ring of cooling nozzles mounted on the inner shroud and discharging adjacent to the :base of the 'blades means defining air metering passages openings in the inner shroud connecting the interior of the jacket to the manifold means defining passages through the inner shroud connecting some of the said cooling nozzles to the manifold and means defining passages in the inner shroud connecting the remainder of the said cooling nozzles to the interior of the jacket bypassing the manifold.

6. A gas turbine engine comprising, in combination,

a turbine wheel blades mounted on the rim of the wheel including stalks connected to the wheel a turbine nozzle including a ring of radially extending vanes disposed upstream of the blades combustion apparatus including a jacket terminating at the nozzle and a combustion liner connected to discharge through the nozzle the nozzle including a hollow outer shroud defining a plenum and a hollow inner shroud defining a manifold the vanes defining passages interconnecting the plenum and the manifold impingement starting nozzles in the outer shroud supplied from the plenum and discharging generally tangentially against the outer end of the blades a ring of cooling nozzles mounted on the inner shroud and discharging adjacent to the blade stalks and wheel rim means defining air metering passage-s openings in the inner shroud connecting the interior of the jacket to the manifold means defining passages through the inner shroud connecting some of the said cooling nozzles to the manifold and means defining passages in the inner shroud connecting the remainder of the said cooling nozzles to the interior of the jacket bypassing the manifold.

References Cited by the Examiner UNITED STATES PATENTS 2,989,848 6/1961 Paiement 39.14 3,019,607 2/1962 Bunger 60-3966 3,085,396 4/1963 Kent 60--39.14

FOREIGN PATENTS 1,122,879 5/ 1956 France.

957,153 5/1964 Great Britain.

MARK NEWMAN, Primary Examiner.

R. D. BLAKESLEE, Assistant Examiner. 

1. AN AIR-COOLED GAS TURBINE COMPRISING, IN COMBINATION, A TURBINE WHEEL BEARING BLADES ON ITS PERIPHERY A TURBINE NOZZLE ADAPTED TO DIRECT MOTIVE FLUID TO THE BLADES COMBUSTION APPARATUS SUPPLYING MOTIVE FLUID TO THE TURBINE NOZZLE INCLUDING AN AIR JACKET SUPPLIED WITH COMPRESSED AIR WHEN THE TURBINE OS IN OPERATION MEANS DEFINING AN AIR CHAMBER TURBINE AIR IMPINGEMENT STARTING NOZZLES SUPPLIED FROM THE CHAMBER TURBINE COOLING NOZZLES SUPPLIED FROM THE CHAMBER LOCATED TO DIRECT COOLING AIR AT THE TURBINE WHEEL VALVED MEANS FOR SUPPLYING COMPRESSED GAS TO THE CHAMBER FOR STARTING THE ENGINE 